1. Field of the Invention
This invention relates generally to memory systems and more particularly to a system and method for write location defect compensation in computer storage media.
2. Description of the Background Art
Storing and retrieving digital information on dependable media is an important consideration for manufacturers, designers and users of computer systems. In magneto-optical storage devices that use flying heads, digital data is written onto and read from the front surfaces of rotating disks of MO storage media. Referring to FIG. 1(a), a plan view of a front surface 112 of a magneto-optical storage medium 110 is shown. In magneto-optical storage devices, digital data is typically written into and read from a series of concentric or spiral tracks 114 located on the surface 112 of storage medium 110. In practice, data is written to storage medium 110 by projecting a laser-generated light beam to heat front surface 112 of storage medium 110. A magnetic coil embedded on a head device then magnetizes the region with either a vertical up or down orientation. These magnetized orientations alter the optical polarization of light reflected back from storage medium 110 during the read process.
During the read process, the digital data is read from the front surface 112 of storage medium 110 by projecting a laser-generated light beam from a flying head onto a selected track 114 while storage medium 110 is rotating, and then sensing the amplitude and polarization of light reflected back from the surface 112 of storage medium 110. Referring now to FIG. 1(b), a cross-sectional view of the FIG. 1 magneto-optical storage medium 110 is shown. In operation, a head device (not shown) is positioned above front surface 112. FIG. 1(b) includes several examples that illustrate possible causes for unreliable or invalid write locations in magneto-optical storage devices. The FIG. 1(b) examples include a corrosion defect 116 and a particulate contamination 118. These examples are presented for the purpose of illustration and defective write locations may alternatively be caused by various other factors.
The FIG. 1(b) examples each significantly alter the data written to and subsequently read from the surface 112 of storage medium 110. Corrosion defect 116 and particulate contamination 118 each affect the recording of magnetic fields during a write operation and also reduce the reflective properties of surface 112. These problems alter the signals of data written to storage medium 110.
As discussed above, corrosion defects 116 and particulate contamination 118 may cause defective write locations in front surface magneto-optical storage devices. From the above discussion, it becomes apparent that MO data is not sufficiently robust to defects. Therefore, an improved system and method is needed for write location defect compensation for computer storage media.